Multiple character gas discharge display device

ABSTRACT

In a multiple segment digit tube, auxiliary anodes are provided near the digits and there is a common main anode. The tube is controlled with negative pulses on the cathode segments and positive capacitively supplied pulses on the auxiliary anodes. All pulses are derived from a single MOST circuit.

' [451 Oct. 15, 1974 United States Patent 1 91 Van Daelen et a1.

[ MULTIPLE CHARACTER GAS DISCHARGE [56] References Cited UNITED STATES PATENTS DISPLAY DEVICE X5 m m H. u. h u" C u a b an SD m hlw a .m Km we .2 d.5 w 8 mW AU .1 TK ML nu I mm mm NM mm x BE 39 a m an .n 3 3 mm m B L C C 8 mmmmm Mn mmmi GmWd nd A e h v nflm l h mmmu e e0.m umHKE m n w .m no H Attorney, Agent, or Firm-Frank R. Trifari; Carl P. Steinhauser [73] Assignee: U.S. Philips Corporation, New

York, N.Y.

[22] Filed: Dec. 21, 1972 ABSTRACT,

In a multiple segment digit tube, auxiliary anodes are 211 Appl. No.: 317,216

provided near the digits and there is a common main Foreign Application Priority Data anode. The tube is controlled with negative pulses on the cathode segments and positive capacitively supplied pulses on the auxiliary anodes. Al

I rived from a single MOST circuit.

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SHEET 1 0F 2 Fig.5

MULTIPLE CHARACTER cAs etscmutor; DISPLAY DEVICE being stacked one on the other with the interposition of strips of insulating material. The invention furthermore relates to a device having such a discharge tube.

A tube of the construction described is known from the published German Pat. application No. 1,948,321. At the area of the matrix groups, apertures are recessed in the strips of insulating material through which apertures all the cathode strips are visible. For each matrix group there is an anode in the form of a grid separated from the cathode strips by a strip of insulation material having the same recesses as the strips between the cathodes.

When the strips of insulation material are sufficiently thin, the drawback that the cathode strips in one character lie in different planes is only small. The advantage is that the strips in one character can overlap each other near the connections so that characters can be observed without interruptions from a wide angle of vision. An advantage of characters constructed from segments is that the voltage difference between cathodes taking part in the discharge and cathodes not taking part in the discharge in the same matrix group can generally be comparatively small, namely approximately 25 volt, as a result of the fact that the cathode segments are not or hardly present in one anothers discharge path. In tubes having characters stacked one on the other, the required voltage difference is higher, namely .50 to 60 volts.

A drawback of the known tube is that the control circuits which have to switch on the anodes have to convey the full discharge current. The same drawback also occurs in multiple tubes having characters stacked one on the other and in single tubes having stacked characters in the case of dynamic control.

It is the object of the invention to avoid this drawback in whichfurther advantages may also be obtained.

According to the invention, in a gas discharge tube for displaying a number of characters in juxtaposed identical matrix groups by means of cathode glow discharge light, in which corresponding cathodes of all the groups, each in the form of a narrow strip, are connected to a continuous connection strip, which stripsare stackedon each other with the interposition of strips of insulation material, said stack with the interposition of an insulation strip is provided on a continuous conductive strip as an anode and a grid-like auxiliary anode is provided between each matrix groupand said common anode with the interposition of insulation stri s.

hen the anode voltage in such a tube is applied intermittently with a recurrence frequency equal to that with which the characters are successively switched on in dynamic control, and with a voltage only slightly higher than the operating voltage of the tube, relative to the operating cathode, it will be sufficient, with a suitably chosen bias voltage of the auxiliary anode and I 2 of the cathode, to use voltage pulses, positive on the auxiliary anode and negative on the cathodes, of 20 to 25 volt each, to cause the desired cathodes to take part in the discharge. Because it is not necessary for the auxiliary anode to convey the discharge current constantly, during the operation of the discharge, to those cathodes which constitute a character, but only so long as is necessary to cause the main anode to take over the discharge current, according to the invention the voltage pulses can be supplied capacitively to the auxiliary anode. According to the invention it is particularly favourable when at the end of the discharge time to a character the relevant auxiliary anode obtains a negative voltage pulse as a result of which the extinction of the discharge to the character is promoted. As a result of this, undesired re-ignition is prevented. ln connection with the above it is thus possible to cause the control of auxiliary anodes and cathodes to take place from one single voltage level. Because the required voltage pulses have such low values and are supplied capacitively to the auxiliary anode, the control circuit for the cathode and for the auxiliary anode may consist of one single integrated MOST circuit.

1n the discharge tube, the matrix groups are preferably covered, on the side remote from. the anode and auxiliary anode and facing the viewer, by means of single or double gauze so as to prevent penetration of the discharge to a wrong matrix group. Such a measure is known per se for multiple digit tubes- The screen of gauze is set up at a fixed voltage-or is connected to the negative terminal of the anode voltage source via a parallel arrangementof, a resistor and a capacitor.

It is also possible'to use a discharge tube according to the invention with the auxiliary anodes as main anodes and the main anode as a screen so that it corresponds substantially to the tube known from the published German Pat. application No.. 1,948,321.

The invention will be described in greater detail with referenceto the accompanying drawing inwhich F 1G. 1 shows diagrammatically the location of the cathode strips in a matrix group as it is observed by the viewer.

FIG. 2 is an exploded perspective view of an eight-,

fold digit tube,

, FIG. 3 is a circuit arrangement for controlling such a tube and FIGS. 4 and 5 show variations of the control elements shownin FIG. 3.

In FIG. 1, sevensegments constitute.a stylised 8, while in addition a central 1 and to the bottom right a decimal point is arranged. The upper and lower segments are denoted by a and d, respectively, and the central horizontal segment by a g. The right-har|d segments are denoted by b and c, the left-hand segments by e and f. The decimal point is denoted by h, the central l by j.

In F IG. 2, the two flat halves of the dischargetube are denoted by l and 2, respectively. These halves are enamelled together with exhaust tubes in the short sides of which tubes only the left-hand one is shown and denoted by 3. The electrode system consists first of all of a tray 4 having flat long flanges 5 and backwards the electrode system Y top of it strips a connected to strip 18, strips d connected to strip 19 and strips g which themselves constitute a part of strip 20. Insulation strip 21 and strip 22 with strips f, strip 23 with strips e are then provided. On top of these are provided an insulation strip 24 on which strip 25 with strips j and strips 26 with'strips h.

The subsequent insulation strip 27 bears the raster and the face plate 8.

Upon stacking, pins are inserted through all the insulation strips and conductive strips for alignment purposes, .which strips are removed after welding the flanges 6 and 7. All the electrodes and the screen are provided with flat electrode supplies 30 which are enamelled in the seam between'the tube halves l and 2. The tube has a gas filling of neon with 1 percent argon of 60 Torr, while mercury is also present in the tube. The cathode strips, the gauze 9 and the auxiliary anode have a thickness of 0. I mm, the anode, the tray 4 and the screen 8 are slightly thicker. The insulation strips are 0.3 mm thick. The segments .a j are 0. l 8 mm wide. The material of the electrodes is chromiumnickel-steel.

FIG. 3 shows the tube diagrammatically with an anode A. auxiliary anodes T1 to T8, cathodes Kalto Ka8 to Kjl to K18 and the screen S. g

The anode A is connected to the connection terminal 52 of the anode voltage source via'a transistor switch;

determines the bias voltage level of the auxiliary an-,

odes. The auxiliary anodes are furthermore connected to a terminal of each time a capacitor C1 to C8 the other terminals of which are connected to the terminal 51 via resistors Rl to R8. These terminals of the capacitors are also connected to the'switches P1 to P8 which can make connections to the voltage source 54.

The transistor switch between the voltage source 52 and the anode A is alternately opened and closed with times of ().l msec and l msec. At the same pace a ring counter is operated which closes the switches P1 to P8 successively for supplying voltage pulses via the capacitors C1 to C8 to the auxiliary anodes T1 to T8. Closing of the switches P] to P8 is synchronized with a coding device which with each of the matrix groups opens the switches Pa to Pj required for switching on the cathode strips a to j.

When one of the switches P1 to P8 is closed, a positive voltage pulse appears at the associated capacitor C1 to C8 which is equal to the voltage difference of terminal 54 relative to terminal 51. This voltage pulse is transmitted to the associated auxiliary anode T1 to T8 which is thus capable of introducing a discharge in the relevant matrix group to the switched-on cathode strips 0 to j. This auxiliary anode discharge is limited by the A a 4 resistors Z1 @128 and taken over by the main anode in which the current becomes larger. The desired cathode strips a to j obtain a negative voltage pulse equal to the voltage difference between the terminals 55 and 51 by opening the relevant switch Pa to P].

In the discharge between the main anode and the cathode strips, the auxiliary anodes assume the plasma potential. When at the end of the closure time of the transistor switch for the anode, in which the discharge extinguishes, the switch P1 to P8 is also opened with the operating character, the auxiliary anode will obtain a negative voltage pulse which promotes the deionisation and hence prevents undesired re-ignition.

The switches P1 to P8 and Pa to Pj can all be integrated in a single most circuit of the P- channel type. The coding device may also be incorporated in said circuit. The value of the passive components in the circuit of FIG.- 3 is: Rato Rj 5 k0 each, R1 to R8 100 k!) each,

Rs 10 kfl, Z1 to Z8 10 MO each, C1 to C8 1 nF each. Relative to terminal 51 the voltages of 52 are 150 volts, of 56 120 volt, of 53 125 volt, of 54 and 55 which are connected together 20 to 25 volt. For simplicity, a possible circuit for stabilising the current .to the cathode strips is omitted. 1 v

In F IGS, instead of the resistor Rs of 10 k0 to terminal 56, a resistor of 10 MD with a parallel capacitor of l0 nF to terminal 51 may be used.

It is shown in FIG. 4 how the system of switches for the auxiliary anodes and the cathode strips is constructed in the case in which a MOST circuit is used of the n-channel type. In this case, one of the switches N1 to N8 must be opened for the selection of an auxiliary anode and one or more of the channels Na to Nj be closed for the selection of the cathode strips.

The ends of the resistors Ra to'Rj not connected to the cathode strips are connected to terminal 55 via diodes Da to Dj.

FIG. 5 shows the system for the case in which a MOST circuit of the complementary type is used. For the auxiliary anodes the channels M1 to M8 are used for inverting the polarity, for the cathodes the channels Ma to M] for inverting the polarity between the terminals 51 and 54 and between the terminals 55 and 51, respectively.

What is claimed is:

l. A multiple-character gas discharge display'device comprising an envelope filled with an ionizable gas, a plurality of narrow strip-shaped cathode elements arranged in a plurality of juxtaposed matrix groups for displaying characters by a cathode glow discharge, a' plurality of stacked connection strips connecting corre sponding cathode elements in each matrix group, strips of insulating material between and separating said cathode connection strips, said strips having apertures therein through which said cathode matrix groups are visible, a continuous conductive strip constituting an .1, including a gauze covering each of the matrix groups on the side remote from the anode and the auxiliary anodes.

3. A device having a gas discharge tube as claimed in claim 1 including means for supplying voltage pulses of 5. A device as claimed in claim 3 including means to supply a negative discharge pulse to the auxiliary anode at the end of the discharge to a matrix group.

6. A device as claimed in claim 3, including switching means for supplying pulses to the auxiliary anodes and the cathodes which form part of a single MOST circuit of the P-channel type, the N-channel type or the complementary type. 

1. A multiple-character gas discharge display device comprising an envelope filled with an ionizable gas, a plurality of narrow strip-shaped cathode elements arranged in a plurality of juxtaposed matrix groups for displaying characters by a cathode glow discharge, a plurality of stacked connection strips connecting corresponding cathode elements in each matrix group, strips of insulating material between and separating said cathode connection strips, said strips having apertures therein through which said cathode matrix groups are visible, a continuous conductive strip constituting an anode at the base of said stacks, a grid-like auxiliary anode between each matrix group and said anode, and an insulation strip between the auxiliary anodes and the conductive strip anode.
 2. A gas discharge display device as claimed in claim 1, including a gauze covering each of the matrix groups on the side remote from the anode and the auxiliary anodes.
 3. A device having a gas discharge tube as claimed in claim 1 including means for supplying voltage pulses of opposite sign to the auxiliary anode and the cathode strips for producing a discharge in a matrix group.
 4. A device as claimed in claim 3, wherein the voltage pulses are capacitively supplied to the auxiliary anodes.
 5. A device as claimed in claim 3 including means to supply a negative discharge pulse to the auxiliary anode at the end of the discharge to a matrix group.
 6. A device as claimed in claim 3, including switching means for supplying pulses to the auxiliary anodes and the cathodes which form part of a single MOST circuit of the P-channel type, the N-channel type or the complementary type. 